concatenation

问题 I want to concat two or more gzip streams without recompressing them. I mean I have A compressed to A.gz and B to B.gz, I want to compress them to single gzip (A+B).gz without compressing once again, using C or C++. Several notes: Even you can just concat two files and gunzip would know how to deal with them, most of programs would not be able to deal with two chunks. I had seen once an example of code that does this just by decompression of the files and then manipulating original and this

问题 I have a DataFrame with multiple rows. Is there any way in which they can be combined to form one string? For example: words 0 I, will, hereby 1 am, gonna 2 going, far 3 to 4 do 5 this Expected output: I, will, hereby, am, gonna, going, far, to, do, this 回答1: You can use str.cat to join the strings in each row. For a Series or column s , write: >>> s.str.cat(sep=', ') 'I, will, hereby, am, gonna, going, far, to, do, this' 回答2: How about traditional python's join ? And, it's faster. In [209]:

问题 I'm using sqlite3 for the moment, and hence concatenation strings using the || operator. At some later date I'd like to shift to MySQL, and hence it would be nice if no changes to the code had to be made. I'd normally use concat() to concatenate in MySQL. Does || work too, or will I have to modify my code? Or is there any other solution? I'm coding in Ruby on Rails 3.1, by the way. 回答1: The || works in MySQL as well but you need to set sql_mode to PIPES_AS_CONCAT . Official Doc Demo: mysql>

问题 I want to concatenate in the middle of an echo to write an if statement, is this possible? Here is what I have. echo "<li class='".if ($_GET["p"] == "home") { echo "active"; }."'><a href='#'>Home</a> </li>"; 回答1: Like this, using the ternary operator: echo "<li class='". (($_GET["p"] == "home") ? "active" : "") . "'><a href='#'>Home</a> </li>"; 回答2: Do like this: echo "<li class='".($_GET["p"] == "home" ? 'active' : '') ."'><a href='#'>Home</a> </li>"; 回答3: echo "<li class='".(($_GET["p"] ==

问题 I try to concatenate .wav audio files in swift. Here is my code : func merge(audio1: NSURL, audio2: NSURL) { var error:NSError? var ok1 = false var ok2 = false var documentsDirectory:String = paths[0] as! String //Create AVMutableComposition Object.This object will hold our multiple AVMutableCompositionTrack. var composition = AVMutableComposition() var compositionAudioTrack1:AVMutableCompositionTrack = composition.addMutableTrackWithMediaType(AVMediaTypeAudio, preferredTrackID:

问题 I have a JSON array coming in from the server with an array of 200 objects each containing another 10 objects that I want to display in a table format. At first I was creating a <tr> for each iteration and using jQuery to append a <td> built from the array values to the <tr> . This was taking around 30 seconds in Chrome and 19 seconds in IE 8. This was taking too long so I tried switching to the Array.join() method, where I would store each string that would make up the entire table in an

问题 Why did the designers of PHP decide to use a full stop / period / "." as the string concatenation operator rather than the more usual plus symbol "+" ? Is there any advantage to it, or any reason at all? Or did they just like to? :o) 回答1: The most obvious reason would probably be that PHP inherits a lot of its syntax from Perl - and Perl uses a dot ( . ) for string concatenation. But, we can delve deeper into it and figure out why this was implemented in Perl - the + operator is most commonly

问题 What is the most efficient way to prepend to a C string, using as little memory as possible? I am trying to reconstruct the path to a file in a large directory tree. Here's an idea of what I was doing before: char temp[LENGTH], file[LENGTH]; file = some_file_name; while (some_condition) { parent_dir = some_calculation_that_yields_name_of_parent_dir; sprintf(temp, "%s/%s", parent_dir, file); strcpy(file, temp); } This seems a bit clunky though. Any help would be appreciated. Thanks! 回答1:

问题 I'm working through Udacity and Dave Evans introduced an exercise about list properties list1 = [1,2,3,4] list2 = [1,2,3,4] list1=list1+[6] print(list1) list2.append(6) print(list2) list1 = [1,2,3,4] list2 = [1,2,3,4] def proc(mylist): mylist = mylist + [6] def proc2(mylist): mylist.append(6) # Can you explain the results given by the four print statements below? Remove # the hashes # and run the code to check. print (list1) proc(list1) print (list1) print (list2) proc2(list2) print (list2)

问题 Is it even possible to concatenate vectors in Rust? If so, is there an elegant way to do so? I have something like this: let mut a = vec![1, 2, 3]; let b = vec![4, 5, 6]; for val in &b { a.push(val); } Does anyone know of a better way? 回答1: The structure std::vec::Vec has method append(): fn append(&mut self, other: &mut Vec<T>) Moves all the elements of other into Self , leaving other empty. From your example, the following code will concatenate two vectors by mutating a and b : fn main() {